Variable displacement compressor

ABSTRACT

A variable displacement compressor includes a compressor housing, a rotary shaft, a lug plate, a swash plate, a hinge mechanism, a supply passage and a bleed passage. The compressor housing includes a pressure control chamber having a front region which extends between the swash plate and the lug plate, and a rear region on the opposite side of the swash plate as viewed from the lug plate. The rotary shaft has an axial bleed passage which forms part of the bleed passage and an inlet which is in communication with the axial bleed passage and opened to the front region of the pressure control chamber. At least one of the swash plate and the rotary shaft has a communication passage. The front region and the rear region of the pressure control chamber are in communication with each other through the communication passage.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent application no. 2006-330899 filed Dec. 7, 2006.

BACKGROUND OF THE INVENTION

The present invention relates to a variable displacement compressor that is operable to adjust the pressure in a pressure control chamber of the compressor thereby to change angle of inclination of a swash plate of the compressor, whereby the displacement of the compressor is controlled.

Japanese Patent Application Publication No. 2004-28090 discloses this type of variable displacement compressor (hereinafter referred to merely as “compressor”). Referring to FIG. 10 showing the compressor of the Publication, it has a housing in which a crank chamber 80 is formed and a shaft 81 rotatably supported by the housing and extending through the crank chamber 80. A rotor 92 is mounted on the shaft 81 in the crank chamber 80. A swash plate 82 is supported by the shaft 81 in the crank chamber 80 in such a way that the inclination angle of the swash plate 82 relative to the shaft 81 is variable. Plural pistons 83 engage with the swash plate 82 through plural pairs of shoes 84, respectively. The housing has formed therethrough plural cylinder bores 94 which receive therein the pistons 83 for reciprocation, respectively.

The housing has a discharge chamber 85 and a suction chamber 86. The discharge chamber 85 and the crank chamber 80 are in communication with each other through a first communication passage 87 and a second communication passage 88. The suction chamber 86 and the crank chamber 80 are in communication with each other through a bleed passage. The bleed passage includes an axial passage 89 formed axially in the shaft 81, a communication hole 90 formed in the shaft 81 so as to communicate with the crank chamber 80 and the axial passage 89 and a third passage 91 communicating with the axial passage 89 and the suction chamber 86. As shown in FIG. 10, the communication hole 90 is located between the swash plate 82 and the rotor 92.

In the above compressor, part of refrigerant gas in the discharge chamber 85 flows into the crank chamber 80 through the first communication passage 87 and the second communication passage 88. The refrigerant gas in the crank chamber 80 flows out thereof from the communication hole 90 to the suction chamber 86 through the axial passage 89 and the third passage 91. Thus, the compressor is operable to adjust the pressure in the crank chamber 80 thereby to change the angle of inclination of the swash plate 82, whereby the displacement of the compressor is controlled.

The refrigerant gas flowing from the discharge chamber 85 to the crank chamber 80 contains lubricating oil. The blow-by gas leaking into the crank chamber 80 through a clearance between the cylinder bore 94 and its corresponding piston 83 also contains lubricating oil. Before the refrigerant gas including the blow-by gas passing through the crank chamber 80 moves into the communication hole 90, the lubricating oil in the gas is supplied to various sliding parts (such as a sliding part between the swash plate 82 and the shoes 84) in the crank chamber 80. Specifically, the lubricating oil in the gas passing through the crank chamber 80 is separated therefrom by the centrifugal force of various rotating parts such as the swash plate 82 and the rotor 92 that are driven to rotate by the shaft 81 and dispersed around the shaft 81, the inner wall surface of the crank chamber 80 and the various sliding parts in the crank chamber 80. Thus, the sliding parts are lubricated by the lubricating oil.

On the other hand, because the lubricating oil in the refrigerant gas is dispersed around the shaft 81, the communication hole 90 and its vicinities are lack of lubricating oil, so that the lubricating oil in the crank chamber 80 does not sufficiently flow into the suction chamber 86 through the communication hole 90, the axial passage 89 and the third passage 91. Therefore, there exists an excessive amount of lubricating oil in the crank chamber 80. When such excessive amount of lubricating oil is stirred by the rotation of the swash plate 82 and the rotor 92, the lubricating oil is heated with the result that its viscosity and lubricity are reduced.

The inlet of the bleed passage through which the refrigerant gas in the crank chamber 80 flows out thereof to the suction chamber 86 may be formed, for example, in a stationary part of the compressor such as the end face of the housing or the cylinder block which forms the crank chamber 80 so that the lubricating oil is less subjected to the influence of the centrifugal force. In such structure, however, an excessive amount of the lubricating oil flows into the suction chamber 86, so that the amount of the lubricating oil in the crank chamber 80 is reduced and the sliding parts of the compressor will be poorly lubricated, accordingly.

The present invention, which has been made in light of the above problems, is directed to a variable displacement compressor which ensures an appropriate amount of lubricating oil in a pressure control chamber of the compressor.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, a variable displacement compressor includes a compressor housing, a rotary shaft, a lug plate, a swash plate, a hinge mechanism, a supply passage and a bleed passage. The compressor housing has a pressure control chamber, a discharge pressure region and a suction pressure region. The rotary shaft has a front end and a rear end. The rotary shaft is rotatably supported at the front end by a front portion of the compressor housing and at the rear end by a rear portion of the compressor housing, respectively. The lug plate is fixed on the rotary shaft in the pressure control chamber. The swash plate is accommodated in the pressure control chamber. The hinge mechanism is provided between the lug plate and the swash plate. The swash plate is directly supported by the rotary shaft and connected to the lug plate through the hinge mechanism so that the swash plate is rotatable in synchronization with the rotary shaft and the lug plate while inclination angle of the swash plate is variable. The supply passage communicates with the discharge pressure region and the pressure control chamber. The bleed passage communicates with the suction pressure region and the pressure control chamber. Pressure in the pressure control chamber is adjusted by supplying refrigerant gas in the discharge pressure region to the pressure control chamber through the supply passage and releasing the refrigerant gas in the pressure control chamber to the suction pressure region through the bleed passage, thereby to change the inclination angle of the swash plate, whereby displacement of the compressor is controlled. The pressure control chamber has a front region which extends between the swash plate and the lug plate, and a rear region on the opposite side of the swash plate as viewed from the lug plate. The rotary shaft has an axial bleed passage which forms part of the bleed passage and an inlet which is in communication with the axial bleed passage and opened to the front region of the pressure control chamber. At least one of the swash plate and the rotary shaft has a communication passage. The front region and the rear region of the pressure control chamber are in communication with each other through the communication passage.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a longitudinal sectional view showing a variable displacement compressor according to an embodiment of the present invention;

FIG. 2 shows the front of a swash plate of the variable displacement compressor of FIG. 1;

FIG. 3 is side view showing the swash plate of FIG. 1;

FIG. 4 shows the rear of the swash plate of FIG. 1;

FIG. 5 is a graph showing relations between oil content percentage and residual oil percentage of various variable displacement compressors;

FIG. 6A is a cross sectional view showing an inlet of a rotary shaft of the compressor and its vicinities according to another embodiment of the present invention;

FIG. 6B is a perspective view showing the inlet of the rotary shaft and its vicinities of FIG. 6A;

FIG. 7 is a fragmentary longitudinal sectional view showing a communication passage according to yet another embodiment of the present invention;

FIG. 8 is a longitudinal sectional view showing a variable displacement compressor according to yet another embodiment of the present invention, wherein the supply passage of FIG. 1 is modified;

FIG. 9 shows a communication passage according to yet another embodiment of the present invention; and

FIG. 10 is a longitudinal sectional view showing a compressor according to the background art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following will describe an embodiment of the variable displacement compressor according to the present invention with reference to FIGS. 1 to 5. The terms “front” and “rear” of the variable displacement compressor as will be used in the following description are indicated by the arrow Y in FIG. 1.

Referring to FIG. 1 showing the variable displacement compressor 10 of the present embodiment in its longitudinal sectional view, it has a compressor housing including a cylinder block 11, a front housing 12 fixed to the front end of the cylinder block 11, and a rear housing 14 fixed to the rear end of the cylinder block 11. Between the cylinder block 11 and the rear housing 14 are interposed a suction valve forming plate 36, a valve plate 13, a discharge valve forming plate 28 and a retainer 33. The cylinder block 11 and the front housing 12 define a pressure control chamber C through which a rotary shaft 15 extends. The rotary shaft 15 is rotatably supported by the cylinder block 11 and the front housing 12.

The rotary shaft 15 includes a first shaft portion 16 in the form of a hollow cylinder having an opening at the rear end thereof and a second shaft portion 17 in the form of a hollow cylinder having openings at the opposite ends thereof and pressed (or inserted) into the first shaft portion 16 so as to form a double-tube structure. An O-ring O is held between the inner circumferential surface of the first shaft portion 16 and the outer circumferential surface of the second shaft portion 17 adjacent to the front end of the second shaft portion 17. An axial supply passage 15 a is formed by the inner peripheral surface of the second shaft portion 17 of the rotary shaft 15 so as to extend in the direction of the axis T of the rotary shaft 15. Further, an axial bleed passage 15 b is formed between the inner peripheral surface of the first shaft portion 16 and the outer circumferential surface of the second shaft portion 17 of the rotary shaft 15.

The first shaft portion 16 of the rotary shaft 15 has an exit passage 16 c which is in communication with the axial supply passage 15 a and opened in facing relation to the front housing 12. The axial supply passage 15 a of the rotary shaft 15 is opened at the rear end of the rotary shaft 15. An inlet 16 d is formed in the first shaft portion 16 of the rotary shaft 15 at a position facing the pressure control chamber C for communication between the axial bleed passage 15 b and the pressure control chamber C. The axial bleed passage 15 b of the rotary shaft 15 is opened at the rear end of the rotary shaft 15.

The front end of the rotary shaft 15 is rotatably supported by the front housing 12. A shaft seal chamber 20 is formed in the front housing 12 between the circumferential surface of the front end of the rotary shaft 15 and the inner peripheral surface of the front housing 12 facing the circumferential surface of the rotary shaft 15. A shaft seal member 21 is provided in the shaft seal chamber 20 for sealing between the circumferential surface of the rotary shaft 15 (or the circumferential surface 16 a of the first shaft portion 16) and the inner peripheral surface of the shaft seal chamber 20 for sealing the rotary shaft 15. The shaft seal member 21 prevents refrigerant gas from leaking out of the compressor 10 from the pressure control chamber C along the circumferential surface of the rotary shaft 15.

The rear end of the rotary shaft 15 is inserted in a shaft hole 11 b formed in the cylinder block 11 and rotatably supported by a bearing 19 provided in the shaft hole 11 b. Thus, the rotary shaft 15 is rotatably supported at the front end thereof by the front portion of the housing (or the front housing 12) and at the rear end thereof by the rear portion of the housing (or the cylinder block 11), respectively.

Between the cylinder block 11 and the valve plate 13 is defined an accommodation hole 11 c in communication with the shaft hole 11 b. The rear end of the second shaft portion 17 of the rotary shaft 15 extends into the accommodation hole 11 c and the axial supply passage 15 a is in communication with the accommodation hole 11 c. A lip seal 37 is accommodated in the accommodation hole 11 c between the outer circumferential surface of the rear end of the second shaft portion 17 and the axial wall surface of the accommodation hole 11 c. The lip seal 37 shuts off the communication between the axial supply passage 15 a and the axial bleed passage 15 b. In addition, the lip seal 37 divides the accommodation hole 11 c into a supply space S1 which is in communication with the axial supply passage 15 a and a bleed space S2 which is in communication with the axial bleed passage 15 b.

A lug plate 22 is fixed on the rotary shaft 15 in the pressure control chamber C for rotation therewith. The lug plate 22 is rotatably supported by a radial bearing 18 provided in the front housing 12. That is, the rotary shaft 15 is rotatably supported by the radial bearing 18 provided in the front housing 12 through the lug plate 22. A thrust bearing 23 is provided between the lug plate 22 and the inner wall surface of the front housing 12. A disc-shaped swash plate 24 is accommodated in the pressure control chamber C. The swash plate 24 has a cylindrical first projection 41 extending rearwardly from the rear surface of the swash plate 24.

A circular sliding plate 42 is arranged around the first projection 41 in such a way that the first projection 41 is inserted in a support hole 42 a formed through the sliding plate 42 at its center. A bearing 43 is interposed between the outer circumferential surface of the first projection 41 and the inner circumferential surface of the support hole 42 a of the sliding plate 42. Another bearing 43 is interposed between the outer peripheral portion of the swash plate 24 and the sliding plate 42 facing the outer peripheral portion of the swash plate 24. The rear face of the swash plate 24 is formed by the rear face 42 c of the sliding plate 42 and the rear end face 41 a of the first projection 41. The swash plate 24 has formed at the center thereof an insertion hole 24 a through which the rotary shaft 15 is inserted.

A hinge mechanism 25 is provided between the lug plate 22 and the swash plate 24. The swash plate 24 is directly supported by the rotary shaft 15 via the insertion hole 24 a and connected to the lug plate 22 through the hinge mechanism 25. By virtue of such arrangement, the swash plate 24 is rotatable in synchronization with the rotary shaft 15 and the lug plate 22, and the swash plate 24 can slide in the direction of the axis T of the rotary shaft 15 while its inclination angle is variable. That is, the swash plate 24 is so arranged that its inclination is variable within a predetermined range of angles between the maximum inclination and the minimum inclination with respect to the plane perpendicular to the axis T of the rotary shaft 15. As is obvious in the art, the maximum inclination is the inclination angle of the swash plate 24 where the maximum displacement of the variable displacement compressor 10 is achieved and the minimum inclination is the inclination angle of the swash plate 24 where the compressor displacement becomes minimum.

The cylinder block 11 has formed therethrough in the direction of the axis T a plurality of cylinder bores 26 (only one of them being shown in FIG. 1) disposed around the rotary shaft 15 at equiangular intervals. Each cylinder bore 26 receives therein a single head piston 27 for reciprocation. The front and rear openings of the cylinder bore 26 are closed by the piston 27 and the suction valve forming plate 36, respectively, and a compression chamber 38 is defined in each cylinder bore 26, whose volume is variable in accordance with the reciprocation of the piston 27 in the cylinder bore 26. The piston 27 engages with the swash plate 24 and the sliding plate 42 through a pair of shoes 29 one of which is arranged on the front side of the swash plate 24 and the other on the rear side thereof, respectively. That is, one of the shoes 29 is disposed between the sliding surface 24 b formed on the outer peripheral portion of the front face 24 c of the swash plate 24 and a spherical surface 27 a of the piston 27, while the other shoe 29 is disposed between the rear face 42 c of the sliding plate 42 and the spherical surface 27 a of the piston 27. The rotation of the swash plate 24 is converted into the reciprocating motion of the piston 27 via the pair of shoes 29 that are disposed in sliding contact with the sliding surface 24 b, the rear face 42 c and also with the spherical surfaces 27 a of the piston 27.

A suction chamber 30 and a discharge chamber 31 are defined by the rear housing 14 and the valve plate 13. The suction chamber 30 and the discharge chamber 31 form a part of the suction pressure region and the discharge pressure region of the compressor, respectively. Specifically, the discharge chamber 31 is provided in a radially inner region of the rear housing 14, and the suction chamber 30 is provided annularly in the rear housing 14 so as to surround the discharge chamber 31. The valve plate 13 has formed therethrough suction ports 32 and discharge ports 34 which are located at positions corresponding to the respective compression chambers 38. The suction valve forming plate 36 has suction valves 36 a for the respective suction ports 32 so that the suction chamber 30 is communicable with the compression chambers 38 through the suction ports 32 and the suction valves 36 a. The suction valve forming plate 36 also has formed therethrough discharge holes 36 b in alignment with the respective discharge ports 34 and the discharge valve forming plate 28 has discharge valves 28 a for the respective discharge ports 34 so that the compression chambers 38 are communicable with the discharge chamber 31 through the discharge holes 36 b, the discharge ports 34 and the discharge valves 28 a. The opening of each discharge valve 28 a is restricted by the retainer 33.

The high-pressure refrigerant gas which is discharged to the discharge chamber 31 is delivered to an external refrigerant circuit 40. The refrigerant gas in the external refrigerant circuit 40 is cooled by a condenser 40 a which forms a part of the external refrigerant circuit 40. Subsequently, the refrigerant is expanded by an expansion valve 40 b and then transferred to an evaporator 40 c where it is evaporated. The refrigerant gas from the evaporator 40 c (which also forms a part of the external refrigerant circuit 40) is drawn into the suction chamber 30 of the compressor 10. The compressor 10 of the present embodiment forms a part of the refrigerant circuit with the external refrigerant circuit 40. An electromagnetically-operated displacement control valve 60 is installed in the rear housing 14.

The rear housing 14 and the cylinder block 11 have formed therein a first passage 61 a for communication between the discharge chamber 31 and the supply space S1 of the accommodation hole 11 c via the displacement control valve 60. The cylinder block 11 and the valve plate 13 have formed therein a second passage 61 b for communication between the bleed space S2 of the accommodation hole 11 c and the suction chamber 30.

As the rotary shaft 15 is driven to rotate by any driving source (not shown), the swash plate 24 is rotated with the rotary shaft 15 thereby to cause the piston 27 to reciprocate in the cylinder bore 26. Refrigerant gas circulating through the external refrigerant circuit 40 and then entering the suction chamber 30 of the compressor 10 is drawn into the cylinder bore 26 via the suction port 32 and the suction valve 36 a to be compressed in the compression chamber 38. The compressed refrigerant gas is discharged into the discharge chamber 31 via the discharge port 34 and the discharge valve 28 a. Refrigerant gas discharged into the discharge chamber 31 is delivered to the external refrigerant circuit 40 (or the condenser 40 a). A part of the discharged refrigerant gas flows as the control gas into the supply space S1 via the first passage 61 a.

The amount of the refrigerant gas supplied to the supply space S1 via the first passage 61 a is adjusted by controlling the opening of the displacement control valve 60. The refrigerant gas supplied to the supply space S1 is then supplied into the axial supply passage 15 a. The refrigerant gas passing through the axial supply passage 15 a flows into the shaft seal chamber 20 through the exit passage 16 c and blown against the shaft seal member 21 in the shaft seal chamber 20. The shaft seal member 21 is lubricated by the lubricating oil contained in the refrigerant gas, maintained in good condition for lubrication, and cooled by the refrigerant gas. Thereafter, the refrigerant gas in the shaft seal chamber 20 flows into the pressure control chamber C through the space between the front housing 12 and the lug plate 22. While passing through the space between the front housing 12 and the lug plate 22, the refrigerant gas is blown against the radial bearing 18 and the thrust bearing 23. Thus, both bearings 18 and 23 are lubricated by the lubricating oil contained in the refrigerant gas, maintained in good condition for lubrication, and cooled by the refrigerant gas. In the present embodiment, the first passage 61 a, the displacement control valve 60, the supply space S1, the axial supply passage 15 a, the exit passage 16 c and the shaft seal chamber 20 cooperate to form a supply passage through which the discharge chamber 31 and the pressure control chamber C are in communication with each other. The refrigerant gas in the discharge chamber 31 is supplied to the pressure control chamber C as the control gas through the supply passage.

The refrigerant gas in the pressure control chamber C flows into the suction chamber 30 through the inlet 16 d, the axial bleed passage 15 b, the bleed space S2 and the second passage 61 b. In the present embodiment, the inlet 16 d, the axial bleed passage 15 b, the bleed space S2 and the second passage 61 b cooperate to form a bleed passage through which the pressure control chamber C and the suction chamber 30 are in communication with each other. The refrigerant gas in the pressure control chamber C is released as the control gas to the suction chamber 30 through the bleed passage.

Depending on the relation between the amount of refrigerant gas supplied into the pressure control chamber C via the supply passage and the amount of refrigerant gas released from the pressure control chamber C via the bleed passage, the pressure in the pressure control chamber C is adjusted and determined. When the pressure in the pressure control chamber C is changed, the pressure difference between the pressure control chamber C and the cylinder bore 26 via the piston 27 is changed thereby to change the inclination angle of the swash plate 24, with the result that the stroke of the piston 27 (or the displacement of the compressor 10) is adjusted.

The following will describe the swash plate 24 more in detail. As shown in FIGS. 1 to 4, the insertion hole 24 a is formed through the swash plate 24 at the center thereof so as to extend in the direction of thickness thereof. The first projection 41 extends from the rear surface of the swash plate 24 so as to surround the insertion hole 24 a. It is noted that the direction of thickness of the swash plate 24 refers to the direction of the swash plate 24 which intersects with an imaginary plane H including the front face 24 c (or the sliding surface 24 b) of the swash plate 24. In the present embodiment, the thickness of the swash plate 24 extends in the direction that is perpendicular to the imaginary plane H. A restricting member 44 is provided in the outer circumferential surface of the rotary shaft 15 for restricting the inclination of the swash plate 24 to determine its minimum inclination angle, as indicated by the chain double-dashed line in FIG. 1.

As shown in FIGS. 2 and 3, a second projection 45 extends from the front face 24 c of the swash plate 24 toward the front housing 12. The second projection 45 is formed in a semicylindrical shape so as to surround a half of the insertion hole 24 a along its peripheral surface. The front face of the swash plate 24 is formed by the front face 24 c and the end face 45 a of the second projection 45. As shown by the solid line of FIG. 1, the maximum inclination angle of the swash plate 24 is restricted and determined by contact of the end face 45 a of the second projection 45 with the rear face 22 a of the lug plate 22. In the present embodiment, the second projection 45 forms a maximum inclination angle restricting portion for restricting the inclination angle of the swash plate 24 to the maximum inclination angle.

As shown in FIG. 1, the pressure control chamber C has a rear region C1 which extends between the rear face of the swash plate 24 (or the rear face 42 c of the sliding plate 42 and the rear end face 41 a of the first projection 41) and the front end face 11 d of the cylinder block 11 facing the pressure control chamber C. The pressure control chamber C also has a front region C2 which extends between the front face of the swash plate 24 (or the front face 24 c and the end face 45 a of the second projection 45) and the rear face 22 a of the lug plate 22. That is, the front region C2 covers a region in the pressure control chamber C between the swash plate 24 and the lug plate 22 and the rear region C1 covers a region on the opposite side of the swash plate 24 as viewed from the lug plate 22.

In this case, the inlet 16 d is opened to the front region C2 irrespective of whether the swash plate 24 is positioned at the maximum inclination angle or minimum inclination angle. As shown in FIGS. 2 to 4, three communication passages 46, each of which passes through the swash plate 24 in the direction of its thickness, are formed around the insertion hole 24 a of the swash plate 24, or around the rotary shaft 15 inserted through the insertion hole 24 a.

As shown in FIGS. 4 and 2, each communication passage 46 has a first opening 46 a which is formed at the end face 41 a of the first projection 41 and opened to the rear region C1 and a second opening 46 b which is formed at the front face 24 c of the swash plate 24 and opened to the front region C2. The second opening 46 b of each communication passage 46 is generally located between the hinge mechanism 25 and the second projection 45. Specifically, the second opening 46 b is located radially inward of the semicylindrical second projection 45 so as to be surrounded thereby. The second opening 46 b being located radially inward of the second projection 45 intends to mean that the second opening 46 b is located between the inner peripheral surface of the second projection 45 and the circumferential surface of the rotary shaft 15 which face each other.

The communication passage 46 passes through the swash plate 24 in the direction of its thickness so that the rear and front regions C1 and C2 in the pressure control chamber C communicate with each other through the passage 46. The communication passage 46 has a circular cross section and its diameter is substantially the same as that of the inlet 16 d throughout its axial length. The communication passage 46 is so arranged that the second opening 46 b is located most adjacent to the outer circumferential surface of the rotary shaft 15 when the swash plate 24 is tilted at its maximum inclination angle position with the end face 45 a of the second projection 45 in contact with the rear face 22 a of the lug plate 22.

The following will describe the operation of the variable displacement compressor 10. A part of the refrigerant gas discharged into the discharge chamber 31 is supplied into the front region C2 of the pressure control chamber C through the first passage 61 a, the displacement control valve 60, the supply space S1, the axial supply passage 15 a, the exit passage 16 c and the shaft seal chamber 20. Blow-by gas leaks from the compression chamber 38 into the rear region C1 of the pressure control chamber C through a clearance between the piston 27 and the cylinder bore 26. A part of the refrigerant gas in the pressure control chamber C flows into the axial bleed passage 15 b through the inlet 16 d toward the suction chamber 30 by the pressure difference between the pressure control chamber C and the suction chamber 30.

Lubricating oil in the refrigerant gas in the front region C2 of the pressure control chamber C is thrown outwardly of the rotary shaft 15 by centrifugal force that is due to the rotation of the rotary shaft 15, the lug plate 22 and the swash plate 24 to be adhered to the inner peripheral surface of the front housing 12 for the pressure control chamber C. Because the blow-by gas also contains lubricating oil, a large amount of lubricating oil is dispersed in the rear region C1. Because the pressure in the rear region C1 is higher than that in the front region C2 that is in communication with the inlet 16 d, the refrigerant gas in the rear region C1 and the lubricating oil in the refrigerant gas are supplied around the rotary shaft 15 in the front region C2 through the communication passage 46 under the influence of the pressure difference between the rear region C1 and the front region C2. Because the second opening 46 b is located between the second projection 45 and the rotary shaft 15, the refrigerant gas supplied into the front region C2 and the lubricating oil in the refrigerant gas remain in a space between the second projection 45 and the rotary shaft 15 without being immediately thrown outwardly from the rotary shaft 15 by the rotation of the rotary shaft 15.

Because the second opening 46 b of the communication passage 46 is located adjacent to the outer circumference of the rotary shaft 15, the refrigerant gas and the lubricating oil in the refrigerant gas which have passed through the communication passage 46 are introduced into the inlet 16 d formed in the rotary shaft 15 at a position between the swash plate 24 and the lug plate 22. The refrigerant gas and the lubricating oil in the refrigerant gas after being introduced into the inlet 16 d flows into the suction chamber 30 through the axial bleed passage 15 b and the bleed space S2. That is, the refrigerant gas and the lubricating oil in the refrigerant gas in the rear region C1 flows into the suction chamber 30 by forming the communication passage 46 in the swash plate 24.

Referring to FIG. 5 showing a graph in which the horizontal axis represents oil content percentage (%) that is the ratio of the volume of lubricating oil to the volume of refrigerant gas circulating through the refrigerant circuit and the vertical axis residual oil percentage (%) that is the ratio of the volume of lubricating oil to the volume of the pressure control chamber C. The oil content percentage is set as low as possible so as to prevent the reduction of refrigeration capacity due to adhesion of lubricating oil to the components of the external refrigerant circuit 40 of the refrigerant circuit including the variable displacement compressor 10, the condenser 40 a, the expansion valve 40 b and the evaporator 40 c while ensuring that various sliding parts in the pressure control chamber C of the variable displacement compressor 10 are lubricated adequately. In the present embodiment, the oil content percentage should preferably be set at N %. On the other hand, the residual oil percentage is set such that generation of abnormal heat due to the presence of an excessive amount of lubricating oil in the pressure control chamber C is prevented while ensuring adequate lubrication of various sliding parts in the pressure control chamber C. In the present embodiment, the residual oil percentage should preferably be set at M %. When the residual oil percentage of the pressure control chamber C is M % with the oil content percentage of the refrigerant circuit including the compressor 10 set at N %, the presence of an appropriate amount of lubricating oil in the pressure control chamber C is ensured.

Referring to FIG. 5, the graph G1 represents the relation between the oil content percentage and the residual oil percentage of the variable displacement compressor 10 according to the present embodiment in which the communication passage 46 is formed in the swash plate 24. The graph G2 represents the relation of a variable displacement compressor in which a passage such as the communication passage 46 is not formed in the swash plate 24 and the refrigerant gas in the front region C2 flows from the inlet 16 d to the suction chamber 30 through the axial bleed passage 15 b as in the case of the background art. The graph G3 represents the relation of a variable displacement compressor in which the refrigerant gas is released to the suction chamber 30 through a bleed passage formed extending from the end face 11 d of the cylinder block 11 facing the pressure control chamber C.

As shown by the graph G1 of FIG. 5, when the oil content percentage is N % in the variable displacement compressor 10 of the present embodiment, the residual oil percentage of the pressure control chamber C is M %. Thus, an appropriate amount of lubricating oil is present in the pressure control chamber C. In the variable displacement compressor of the graph G2, when the oil content percentage is N %, the residual oil percentage is much higher than M % of the graph G1. This means that an excessive amount of lubricating oil remains in the pressure control chamber C because the lubricating oil does not flow sufficiently from the pressure control chamber C. In the case of the variable displacement compressor of the graph G3, when the oil content percentage is N %, the residual oil percentage is much lower than M % of the graph G1. Thus, necessary amount of lubricating oil fails to remain in the pressure control chamber C because an excessive amount of lubricating oil flows from the pressure control chamber C.

According to the embodiment, the following advantageous effects are obtained.

(1) According to the embodiment, the rotary shaft 15 has formed therein the inlet 16 d which is opened to the front region C2. In addition, the swash plate 24 has formed therein around the insertion hole 24 a of the swash plate 24 a plurality of the communication passages 46 through which the rear region C1 and the front region C2 in the pressure control chamber C are in communication with each other. The communication passages 46 enable the refrigerant gas and the lubricating oil in the refrigerant gas in the rear region C1 to be supplied into the front region C2. Even when the lubricating oil in the refrigerant gas in the front region C2 is thrown outwardly of the rotary shaft 15 by the centrifugal force of the rotary shaft 15, the lubricating oil can be supplied into the inlet 16 d by the communication passages 46 formed from the rear region C1 to the front region C2. Therefore, the lubricating oil can be released from the pressure control chamber C to the suction chamber 30, so that the amount of lubricating oil in the pressure control chamber C is prevented from becoming excessive and, therefore, an appropriate amount of lubricating oil is maintained in the pressure control chamber C. Consequently, the stirring of an excessive amount of lubricating oil in the pressure control chamber C by the rotation of the swash plate 24 and other rotating parts is prevented, so that the generation of heat and hence the viscosity of the lubricating oil is reduced and the lubricating performance of the lubricating oil is maintained, accordingly.

(2) The communication passages 46 which are formed extending through the swash plate 24 in the direction of its thickness and around the insertion hole 24 a of the swash plate 24 enables a larger amount of refrigerant gas and lubricating oil in the refrigerant gas to be supplied from the rear region C1 to the front region C2, as compared with the background art wherein the refrigerant gas in the rear region C1 is supplied into the front region C2 through a space between the outer circumferential surface of the swash plate 24 and the inner peripheral surface of the front housing 12. Although it is difficult for the refrigerant gas and the lubricating oil in the refrigerant gas to move from the rear region C1 to the front region C2 because of the wobbling motion of the swash plate 24 in the axial direction of the axis T of the rotary shaft 15, the variable displacement compressor 10 of the present embodiment enables the refrigerant gas and the lubricating oil in the refrigerant gas to be supplied smoothly from the rear region C1 to the front region C2.

(3) The second opening 46 b of each communication passage 46 is located between the hinge mechanism 25 and the second projection 45 which determines the maximum inclination angle of the swash plate 24. Therefore, the refrigerant gas and the lubricating oil in the refrigerant gas supplied from the second opening 46 b into the front region C2 are less subjected to the centrifugal force caused by the rotation of the second projection 45 and the hinge mechanism 25, which makes it easier for the refrigerant gas and the lubricating oil in the refrigerant gas to be introduced into the axial bleed passage 15 b through the inlet 16 d.

(4) The second opening 46 b of each communication passage 46 is located at positions in a space between the second projection 45 of the swash plate 24 and the rotary shaft 15. This prevents the refrigerant gas and the lubricating oil in the refrigerant gas supplied from the second opening 46 b into the front region C2 through the communication passages 46 from being blown immediately outwardly from the above space, which enables the lubricating oil to remain in the space around the rotary shaft 15. Compared with a case where there is provided no such openings as the second opening 46 b of each communication passage 46, the refrigerant gas and the lubricating oil in the refrigerant gas supplied from the second opening 46 b into the front region C2 through the communication passages 46 are introduced efficiently into the axial bleed passage 15 b through the inlet 16 d.

(5) The second opening 46 b of each communication passage 46 is moved closest to the inlet 16 d when the inclination angle of the swash plate 24 becomes maximum. In addition, the second opening 46 b of each communication passage 46 is formed adjacent to the insertion hole 24 a for the rotary shaft 15. Therefore, the refrigerant gas and the lubricating oil in the refrigerant gas supplied from the rear region C1 into the front region C2 immediately flows through the inlet 16 d.

The above embodiment may be modified in various ways as exemplified below.

Referring to FIGS. 6A and 6B, the rotary shaft 15 may have a cutout portion 16 f adjacent to the inlet 16 d extending in the direction of the axis T of the rotary shaft 15. As shown in FIG. 6B, the cutout portion 16 f is formed deeper toward the inlet 16 d, so that a collision portion 16 g is formed adjacent to the inlet 16 d for allowing the refrigerant gas and the lubricating oil in the refrigerant gas to collide thereagainst and a collecting portion 16 h is also formed adjacent to the inlet 16 d. The collecting portion 16 h extends so as to intersect with the rotational direction of the rotary shaft 15 and connected to the collision portion 16 g. By so constructing the rotary shaft 15, the refrigerant gas and the lubricating oil in the refrigerant gas supplied to the cutout portion 16 f in the front region C2 through the communication passages 46 are guided toward the inlet 16 d by the cutout portion 16 f and allowed to collide against the collision portion 16 g to be introduced into the inlet 16 d. During the rotation of the rotary shaft 15, the refrigerant gas and the lubricating oil in the refrigerant gas are collected by the collecting portion 16 h and introduced into the inlet 16 d. Compared with a case where there is provided no such portions as the cutout portion 16 f, the collision portion 16 g and the collecting portion 16 h adjacent to the inlet 16 d, efficiency with which the lubricating oil released from the pressure control chamber C is improved.

Referring to FIG. 7, the rotary shaft 15 may have formed in the outer circumferential surface of the first shaft portion 16 a groove extending from the rear region C1 to the front region C2. The groove of the rotary shaft 15 provides a communication groove 58 through which the rear region C1 and the front region C2 are in communication with each other. The communication groove 58 serves as a communication passage of the present invention. As shown in FIG. 7, the communication groove 58 is connected to the inlet 16 d for communication therewith. Therefore, the rear region C1 and the inlet 16 d are in communication with each other through the communication groove 58. Because in this structure the refrigerant gas and the lubricating oil in the refrigerant gas in the rear region C1 are directly supplied into the inlet 16 d, the lubricating oil is released to the suction chamber 30 more efficiently as compared with a case where a groove such as the communication groove 58 is not formed in the rotary shaft 15.

Referring to FIG. 8, the cylinder block 11 may have formed therethrough a passage 61 c which communicates with the pressure control chamber C on one hand and the displacement control valve 60 on the other. The discharge chamber 31 and the pressure control chamber C may be in communication with each other through the first passage 61 a and the passage 61 c which cooperate to form the supply passage. This modified embodiment of the variable displacement compressor 10 may dispense with the second shaft portion 17 and the axial supply passage 15 a of the rotary shaft 15, the lip seal 37 and the exit passage 16 c of the preferred embodiment.

As shown in FIG. 9, the swash plate 24 may have grooves formed in the inner peripheral surface of the swash plate 24 which forms the insertion hole 24 a, extending through the swash plate 24 in the direction of its thickness. The grooves of the swash plate 24 provide communication grooves 59 through which the rear region C1 and the front region C2 are in communication with each other. The communication grooves 59 serves as a communication passage of the present invention.

A sleeve may be interposed between the inner peripheral surface of the insertion hole 24 a of the swash plate 24 and the outer circumferential surface of the rotary shaft 15. With the sleeve provided between the swash plate 24 and the rotary shaft 15, the swash plate 24 is directly supported by the rotary shaft 15 and leakage of the refrigerant gas passing from the rear region C1 to the front region C2 through the insertion hole 24 a is restricted.

The number of the communication passages 46 of the swash plate 24 may be one or two. Alternatively, the number of the communication passages 46 of the swash plate 24 may be four or more.

The communication passages 46 having the same diameter as the inlet 16 d in the above embodiment may be modified so as to have any different diameter.

In addition to the communication passages 46 of the swash plate 24, a groove may be formed in the outer circumferential surface of the first shaft portion 16 so as to extend from the rear region C1 to the front region C2. The groove of the first shaft portion 16 forms a communication groove through which the rear region C1 and the front region C2 are in communication with each other. Alternatively, in addition to the communication passages 46 of the swash plate 24, grooves may be formed in the inner peripheral surface of the insertion hole 24 a of the swash plate 24 so as to extend through the swash plate 24 in the direction of its thickness. The grooves of the swash plate 24 provide communication grooves 59 through which the rear region C1 and the front region C2 are in communication with each other.

A groove may be formed in the outer circumferential surface of the first shaft portion 16 so as to extend from the rear region C1 to the front region C2. The groove of the first shaft portion 16 forms a communication groove through which the rear region C1 and the front region C2 are in communication with each other. In addition, grooves are formed in the inner peripheral surface of the insertion hole 24 a of the swash plate 24 so as to extend through the swash plate 24 in the direction of its thickness. The grooves of the swash plate 24 provide communication grooves 59 through which the rear region C1 and the front region C2 are also in communication with each other.

The second opening 46 b of each communication passage 46 may be formed in other position than between the second projection 45 and the rotary shaft 15, for example, between the hinge mechanism 25 and the rotary shaft 15.

Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims. 

1. A variable displacement compressor comprising: a compressor housing having a pressure control chamber, a discharge pressure region and a suction pressure region; a rotary shaft having a front end and a rear end, wherein the rotary shaft is rotatably supported at the front end by a front portion of the compressor housing and at the rear end by a rear portion of the compressor housing, respectively; a lug plate fixed on the rotary shaft in the pressure control chamber; a swash plate accommodated in the pressure control chamber; a hinge mechanism provided between the lug plate and the swash plate, wherein the swash plate is directly supported by the rotary shaft and connected to the lug plate through the hinge mechanism so that the swash plate is rotatable in synchronization with the rotary shaft and the lug plate while inclination angle of the swash plate is variable; a supply passage communicating with the discharge pressure region and the pressure control chamber; and a bleed passage communicating with the suction pressure region and the pressure control chamber; wherein pressure in the pressure control chamber is adjusted by supplying refrigerant gas in the discharge pressure region to the pressure control chamber through the supply passage and releasing the refrigerant gas in the pressure control chamber to the suction pressure region through the bleed passage, thereby to change the inclination angle of the swash plate, whereby displacement of the compressor is controlled, wherein the pressure control chamber has a front region which extends between the swash plate and the lug plate, and a rear region on the opposite side of the swash plate as viewed from the lug plate, wherein the rotary shaft has an axial bleed passage which forms part of the bleed passage and an inlet which is in communication with the axial bleed passage and opened to the front region of the pressure control chamber, and wherein at least one of the swash plate and the rotary shaft has a communication passage, the front region and the rear region of the pressure control chamber being in communication with each other through the communication passage.
 2. The variable displacement compressor according to claim 1, wherein the communication passage is formed so as to pass through the swash plate in the direction of thickness thereof.
 3. The variable displacement compressor according to claim 1, wherein the communication passage has a circular cross section and its diameter is substantially the same as that of the inlet.
 4. The variable displacement compressor according to claim 1, wherein the swash plate has an insertion hole through which the rotary shaft is inserted, wherein the communication passage is provided by a groove, which is formed in an inner peripheral surface of the insertion hole of the swash plate so as to extend through the swash plate in the direction of thickness thereof.
 5. The variable displacement compressor according to claim 1, wherein the communication passage is provided by a groove, which is formed in an outer circumferential surface of the rotary shaft and communicates with the inlet.
 6. The variable displacement compressor according to claim 1, wherein the rotary shaft has an axial supply passage and an exit passage which is in communication with the axial supply passage and opened in facing relation to the front portion of the compressor housing, wherein the axial supply passage and the exit passage form part of the supply passage.
 7. The variable displacement compressor according to claim 1, wherein the compressor housing has a cylinder block and a front housing which define the pressure control chamber, wherein the cylinder block has therethrough a passage which communicates with the pressure control chamber, wherein the passage forms part of the supply passage.
 8. The variable displacement compressor according to claim 1, wherein the rotary shaft further comprises: a cutout portion adjacent to the inlet extending in the direction of an axis of the rotary shaft, wherein the cutout portion is formed deeper toward the inlet; a collision portion formed adjacent to the inlet for allowing the refrigerant gas and lubricating oil contained in the refrigerant gas to collide thereagainst; and a collecting portion also formed adjacent to the inlet, wherein the collecting portion extends so as to intersect with a rotational direction of the rotary shaft and connected to the collision portion.
 9. The variable displacement compressor according to claim 1, wherein a maximum inclination angle restricting portion extends from the swash plate, wherein maximum inclination angle of the swash plate is restricted by contact of the maximum inclination angle restricting portion with the lug plate, wherein an opening of the communication passage opened to the front region is located between the maximum inclination angle restricting portion and the hinge mechanism.
 10. The variable displacement compressor according to claim 9, wherein the opening of the communication passage is located between the maximum inclination angle restricting portion and the rotary shaft. 